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Imagine waking up in the morning to find that your skin has a bluish tinge. When you go to the doctor, you discover you have green blood. This isn’t a superpower or magical potion, but it’s a rare blood disorder known as sulfhemoglobinemia. It occurs when there is a lot of sulfhemoglobin (SulfHb) i.e., sulfur-mixed hemoglobin cells in the blood. The pigment is a greenish derivative of the normal hemoglobin. Even if there is only a little bit of sulfur,  it can still cause cyanosis, a discoloration of skin color indicating excess amounts of deoxygenated blood passing through the capillaries. It was first described in medical literature in the 19th century by Miller involving a family with congenital sulfhemoglobinemia. It was also mentioned by Westphal and Azen in 1938 which discussed the oxidation of normal hemoglobin to sulfhemoglobin in rats with jejunal pouches. The term “sulfhemoglobinemia” wasn’t used until the 20th century, with a surge of scientific publications in 1960 and 1970. 

As mentioned, cyanosis is an indication of lack of oxygen in the blood which is usually caused by several conditions of the body like Respiratory Failure, Pulmonary Embolism, or a lung or heart disease. Cyanosis is only a pathological sign, not a disease itself. Having said that, Cyanosis is not life-threatening by itself, but it may be a serious indication of a life-threatening situation.  There are three types of cyanosis – central cyanosis, circumoral cyanosis, and peripheral cyanosis. Central cyanosis is when several parts of the body including hands and feet are discolored, Circumoral cyanosis is when only the mouth and lips turn blue, and Peripheral cyanosis is when toes, feet, hands, and fingers turn blue. Central cyanosis is the most dangerous type of cyanosis and to note, it can be an indication of severe blood, lung, and heart conditions. Another point to note is – when people with darker skin get cyanosis, the discoloration is white instead of blue. For all types of cyanosis, it is recommended to see a doctor for guidance and treatment. 

A famous case of sulfhemoglobinemia was in St Paul’s Hospital in 2007. A 42-year-old white Canadian had been admitted due to developed nerve damage to his knees after falling asleep in a sitting position. He was a smoker, and his medical history included chronic shoulder pain and migraine headaches, as well as Sumatriptan (a medicine) for his migraines. Further, he had a high Creatine Kinase concentration and rapid heartbeat. The toxicology screen showed no warnings, and he was fine to go through surgery. The doctors, Dr. Alana Flexman, Dr. Stephan Schwarz and Dr. Giuseppe Del Vicario in the operating room decided to do fasciotomies, a procedure where the tissue is cut to relieve pressure. When the catheter was placed on his radial artery, the blood came out green, but the doctors believe it was because of the Sumatriptan, which has a lot of sulfur molecules in it. The man was then advised to stop taking his medication, and gradually the trace of Sulfhemoglobin in his blood vanished after 5 weeks. The cause of Sulfhemoglobinemia in this was determined to be due to the medicine he was taking (McVean, 2019). But this is NOT the only cause of Sulfhemoglobinemia overall.   

Other than acquired Sulfhemoglobinemia, there’s also been news of another type of Sulfhemoglobinemia called Neonatal Sulfhemoglobinemia, where sulfhemoglobin is acquired in a baby. There’s also methemoglobinemia which causes a rustic brown discoloration, and is caused by the presence of methemoglobin. 

Research is still in progress on these rare conditions to determine the causes and impacts of this condition, and further the treatment requirement. 

Resources: 

1. “Sulfhemoglobinemia.” Wikipedia, Wikimedia Foundation, 9 Nov. 2024, en.wikipedia.org/wiki/Sulfhemoglobinemia.
2. Crampton, Linda. “Blood Color in Humans and Animals: Meaning and Function.” Owlcation, Owlcation, 2 Dec. 2012, owlcation.com/stem/Blood-Color-in-Humans-and-Animals-Meaning-and-Function.
3. There’s a condition that can cause human blood to turn green. (n.d.). Office for Science and Society. https://www.mcgill.ca/oss/article/did-you-know-health/theres-condition-can-cause-human-blood-turn-green
4. Britannica, The Editors of Encyclopaedia. “sulfhemoglobinemia”. Encyclopedia Britannica, 25 May. 2016, https://www.britannica.com/science/sulfhemoglobinemia.  Accessed 28 September 2024. 
5. Sulfhemoglobinemia – WikEM. (2017). Wikem.org. https://wikem.org/wiki/Sulfhemoglobinemia 
6. The Unusual Case Of The Man With The Green Blood. (2014, August 27). Science 2.0. https://www.science20.com/cash/the_unusual_case_of_the_man_with_green_blood
7. Gharahbaghian, L., Massoudian, B., & DiMassa, G. (2009). Methemoglobinemia and Sulfhemoglobinemia in Two Pediatric Patients after Ingestion of Hydroxylamine Sulfate. Western Journal of Emergency Medicine, 10(3), 197–201. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2729224/
8. Murphy, K., Ryan, C., Dempsey, E. M., O’Toole, P. W., Ross, R. P., Stanton, C., & Ryan, C. A. (2015). Neonatal Sulfhemoglobinemia and Hemolytic Anemia Associated With Intestinal Morganella morganii. Pediatrics, 136(6), e1641–e1645. https://doi.org/10.1542/peds.2015-0996
9. Sulfhemoglobinemia – an overview | ScienceDirect Topics. (n.d.). Www.sciencedirect.com. https://www.sciencedirect.com/topics/medicine-and-dentistry/sulfhemoglobinemia
10.  Soderstrom, M., Foster, D. V., Hamidi, Z. S., Anderson, J. T., Soderstrom, M., Foster, D. V., Hamidi, Z. S., & Anderson, J. T. (2023). Sulfhemoglobinemia in a 53-Year-Old With a History of Phenazopyridine Misuse. Cureus, 15(6). https://doi.org/10.7759/cureus.40944
11.  Seltzer, J. A., Irvan Bubic, Winkler, G. A., Friedman, N. A., Bagby, J., Tomaszewski, C. A., Clark, R. F., Kreshak, A., & Lasoff, D. R. (2022). Sulfhemoglobinemia and methemoglobinemia following acetaminophen overdose. Toxicology Reports, 9, 1725–1727. https://doi.org/10.1016/j.toxrep.2022.08.011
12. Entry – 185460 – SULFHEMOGLOBINEMIA, CONGENITAL – OMIM. (2025). Omim.org. https://www.omim.org/entry/185460
13. George, Ashish, and Danielle Goetz. “A Case of Sulfhemoglobinemia in a Child with Chronic Constipation.” Respiratory Medicine Case Reports, Elsevier BV, Jan. 2017, https://doi.org/10.1016/j.rmcr.2017.03.009. Accessed 6 Oct. 2023.
14. Methemoglobin and Sulfhemoglobin, Blood – Logan Health Medical Center Laboratory Test Catalog. (2025). Testcatalog.org. https://logan.testcatalog.org/show/MET-SUL